Filter arrangement for wire program-distribution circuits



March 9,1926. 1,575,659

M. E. STRIEBY FILTER ARRANGEMENT FOR WIRE PROGRAM DISTRIBUTION cIncuTTs Filed'sept. 7, 192:

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MAURICE E. STRIEBY, 0F MILLBRN, NEW JERSEY, ASSIGNOR TO AMERICAN TEIE- II-IONE AND 'IELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

FILTER ARRANGEMENT FOR WIRE PROGRAM-DISTRIBUTION CIRCUITS;

Application fil-ed September 7, 1923. Serial No. 661,483.

To all 'whom it may concer/n.'

Be it known that I, MAURICE E. Srninnv,

residing at Millburn, in the county of Es sex and State of New Jersey, have invented certain Improvements in Filter Arrangements vfor lVire Prograin-Distribution'Circuits, .of which the following is a specificat-ion.

This invention relates to program dis-V tribution systems and more particularly to systems employing telephone subscribersbrought to Vthe bus-bars leading to the pro-V gram station b'y means of a cheap and economical filtering arrangement. In order to render the filtering arrangement inexpensive it is proposed to include only a part of each of the filters inthe individual circuits associated with the subscribers lines and substitute for the remainder of each of the filters a common filter element included in the bus-bar circuit, which common filter element will cooperate with the filter element in each subscribers line to act as a complete filter foreach line. Another objectof the invention is to provide-a circuit arrangement. whereby when one subscribers line provided with theprogram service is connected forl telephonie purposes with another subscribers line'which is not provided with program service, the program currents will be pre-vented from being transmitted lto said other subscribers'line.

The invention may now, be more fully understood by referenceto the following detailed description when read in connection with the accompanying drawing, Figure 1 of which shows vschematically the arrangement of the filters for segregating the subscribers lines, Figs. 2 and?) of which show two forms of filter structure to be employed inconnection with the circuit of Fig. 1, Figs. 4; and 5 .of whichy are diagrams illustrating the principles of the filter arrangement and Figs. 6 and 7 of which illustrate arrangements for preventing program transmission from being transmitted' to a line not subscribing tothe service when said line ris connected telephonically with a line` subscribing to the service.

Referring to Fig. 1, L1, L2, L3 and L4 designate ordinary telephone subscribersk lines terminating at the central office atl a 4` distributing frame X through `which vthe lines may be connected `to the ordinary cen-k tral ofiice apparatus whereby connectionsv are made between' different subscribers. In

order that the lines may be provided with the program service connections are then made from the frame through circuits such as 11, 12, 18 and 14 tobus-bars lOconnected to a common source of carrier supply VS. The connections 11, 12, 13 and 14 directly interconnect the lines so that normally the indii'lidual operation of the lines at voice vfrequencies would be Vinterfered with. In order to prevent this filters may beincluded in the connections 11, 12, 13 and 14, these filters being arrangedto suppress voice frequencies but to permit the carrier i frequencies from the to all of the lines.

As it would be expensive to provide a filter for each individual line sufficientto give the required degree of attenuation for program source to' pass voice frequencies it is `proposed, in accords" ance with the present invention, toprovide a common filter element inthe busb'ar circuit and individual filter elements, such as F1, F2, F3 and FQ, in the circuits leading to each of the lines,/the individual elements being so related tothe common element that the latter cooperates with any given individual element to constitute a filter for the particular line circuit vwith which the indi vidualv elementl is associated. By this ar. rangement the filter apparatus individual'to the line may be made much cheaper.

Fig. 2 shows one possible arrangement of the filters. densersY are included and also va shunt in- Vductance to complete `the filter element.

Series capacities should also be includedl on the other side of the inductance. These ca'- 10o y In the bus-bar 'circuit series coni' series capacities in the. individual line to act as a high pass filter', passing the program currents to the line but preventing voice frequencies from, being; transmitted from one line to'another through the-bns-bars.

The manner in which the common element and individual element ofthe filter cooper-l ate to constitute a single filter will be clear from Fig. t, which shows a circuit arrangementequivalent to that of Fig. 2.. Here. the shunt. inductance and the condensers in the full lines to the left correspond' tothe common. filter. element' ofY the carrier supply while thetwo condensers in the fulllines to the right coi-respondio the condensers in the individual line. Considering this` bart of the. circuit. alone it is obvious that the arrangement, ifv properly proportioned, will act. asa. high pass filter.

Thel connection of additionalzlines with series condensers to the bus-bars merely amounts to connecting one terminal of each of a number of condensers to) the. opposite terminalsv of" theV shunt inductance and it has been found' that if4 the elements are properliy proportioned' the connection; of additional condensers as indicated in. dotted lines in Fig. 4 does not interfere witht the operation ofthe arrangement shownin full lines an ordinary, high pass. filter... Consequently, each of the subscribers2A lines will be segregated from the other at voicefrequencies by the arrangement shown.

Amodifi'ed. arrangement is shown in Fig. 3, inwhich theV filter. is provided with a series elementcomprising condenser and' intductance in series thus making a band pass lter.; vThe common part of' the filter, simi."- larlly.,.i`s made up of a shunt inductance and a. series. element ofthe type just described while. another series .element of' the same type. is included' in each subscribers lead. rllhe fact. that. the common element will cooperate with any given individualelement to constitute a bandpass filter for that circuit willbe obvious. from the diagranrof' Fig. 5, which.. shows the common element and' one individuall element. in heavy lines.y These two elements corresponding to a well known type of Campbelllband pass filter. The connectioni ofI other branches having inductances. andca-pacities as shown in dotted lines, it has been demonstrated, does not interfere with. the. operation of the part shown.. in heavy lines as a' filter.

A subscriber receiving program transmissionv inthev above manner can use his telephone inthe normalv way without any interference. Incase, however,.the person with wholnhe istalking should at any time connect-Y suitable receiving apparatus to his own telephone line. he would' beable. also.v to. receivethe program transmission If it is desired to4 avoid this it may be done by inserting a low pass'filter or band elimination filter in. each subscriber-s line, as illustrated in Fig. G at' Fl and-FZ. Here, Ll andL2 designate the two subscribers lines terminating; at' central office inv the usualt jacks J, and d'2.. Connections ll and. l2. pass through the indivdual filter elements F1 and F2 to the bus-bars, which inY turn have a. common filter element F included therein, as in Fig. l. The low pass filters li"1 and F, are connected in the individual subscribers lines as shown between the connections l1 and 12 and. the jacks Jfl and J2, thereby preventing the transmission' of the program frequencies to other lines which may be4 connected tele-V phonically to the lines L1 and L2 throughthe usual operators cord. circuit.

A more economical way of accomplishingk the same result is to provide a common filter l!" inthe operators cord circuit C, as shown in Fig. 7. By including the filter in the cord circuit which is common to a plurality of linesa very much smaller number of filters may be providedv for accomplishing the same results as are attained by the arrangement of lfig.. 6.

It will be obvious. thatthe general principles herein disclosed maybe embodied in many other organizations'widely different from. those illustrated without departing from the spirit of the invention as defined in'l the appended claims.

lhat is claimed" is t.

l. A transmissionv system comprisin(Y a common transmissiony path, a. plurality o "individual transmission paths associated? therewith and means to segregate the individual paths from eachother atccrtain frequencies 'comprising a common filter element in the commonl transmission path and. individual filter elements in the individual paths, each individual element being sorelated to the common element that the twor cooperate to form a bandlilter transmitting. a band of frequencies through the individual path with substantially uniform attenuation'. while substantially suppressingthe frequencies lying without the band. l

2. A transmission system comprising a common transmission circuit, a pluralityy of individualA transmission' circuits associated therewith, a common filter element inv the common circuitand individual filterelements in the individual circuits, each. individual element being so related to' the common element that the two functionv as al high pass filter for transmitting frequenciesabove a lower. cut-off'point while substantially suppressing frequenciesvlying below saidI point.

A transmission' system. comprising a common transmission circuit, a plurality of individnal transmission circuits associated therewith, a. filter element' included in the common transmission. circuit. comprising a shunt'impedance and a series impedance and f individual filter elements-in each of theindividual circuits comprising series impedances, the series impedance of each individual circuit being related to the series and shunt impedances ot the common circuit so that they cooperate to constitute a band tilter which passes with substantially uniform attenuation a band of frequencies while suppressing frequencies lying without the band.

il. A program distribution system comprising a program source, bus-bars connected thereto, a plurality of subscribers lines leading to switching arrangements for interconnecting the' lines telephonically, independent connections from subscribers lines to said bus-bars, a common filter element in the busbars and individual lilter elements in the connections of the subscribers lines, each individual element coopera-ting with the common iilter element to constitute a iilter for passing a band of frequencies to the subscribers lines and suppressing the frequencies lying without the band.

5. A program distribution system Comprising a program source, bus-bars connected thereto, a plurality of subscribers lines leading to switching arrangements for interconnecting the lines telephonie-ally, independent connections from subscribers lines to said bus-bars, a commoniilter element in the busbars and individual filter elements in the connections of the subscribers lines, each individual element cooperating with the common filter element to constitute a high pass filter for transmitting program frequencies to the corresponding subscribers line while preventing ordinary telephonie frequencies from being transmitted from one subscribers line to another through the bus-bar connection.

6. A program distribution system comprising a program source, bus-bars connected thereto, a plurality of subscribers lines tern'iinating at an exchange and switching arrangements for interconnecting the lines for telephonie purposes, independent connections from the lines to the bus-bars, means in said connections to prevent telephonie transmission from one line to another through the bus-bars while permitting the transmission of program currents from the bus-bars to the line and means to prevent the transmission ofpprogram currents from one line to another line which is interconnected therewith for ordinary telephone conversation.

7. A program distribution system comprising a program source, bus-bars connected thereto, a plurality of subscribers lines terminating at an exchange and switching arrangements for interconnecting the lines for telephonie purposes, independent connections from the lines to the bus-bars, means in said connections to prevent telephonie transmission from one line to another through the bus-bars while permitting the transmission of program currents from the bus-bars to the line and means to prevent the transmission of program currents from one line to another line which is interconnected therewith for ordinary telephone conversation, said means comprising a filter associated with one of said lines beyond its connection to the bus-bars.

8. A program distribution system comprising a program source, bus-bars connected thereto, a plurality of subscribers lines terminating at an exchange and switching arrangements for interconnecting the lines for telephonie purposes, independent connections from the lines to the bus-bars, means in i said connections to prevent telephonie transmission rom one line to another through the bus-bars while permitting the transmission of program currents from the bus-bars to the line and means to prevent the transmission lof program currents from one line to another line which is interconnected therewith for ordinary telephone conversation, said means comprising a link circuit for eiecting the ordinary telephonie connections and having a filter therein to suppress program currents.

In testimony, whereof, I have signed my name to this specification this 5th day of September, 1923.

MAURICE E. STRIEBY. 

